Effect of deformation temperature on high strain rate superplastic properties in PM 2024AI-Fe-Ni alloys

High strain rate superplastic properties of high strength PM 2024Al-3Fe-5Ni alloys with or without 0. 3 mass % Zr addition have been investigated at a wide testing temperature range of 673K- 793K. The alloys were fabricated by an air atomization technique, followed by extrusion at 623 K and warm rolling at 523K. After the warm rolling, these alloys exhibited ultrafine grained matrix structure. Heating rate to the testing temperatures influenced the superplastic properties of the warm rolled alloy sheets remarkably. After the slow heating (0. 8K/s) up to the testing temperature, PM 2024Al-3Fe-5Ni alloy showed the relatively low maximum elongation of about 250% (m=0. 35) at a strain rate of 3 s^-1 even at 773K, which is very close to the solidus temperature of the matrix alloy. However, in the case of the rapid heating rate (2. 6K/s) condition, the superplastic properties were improved remarkably at the temperature range between 713K and 773K, due to the suppression of microstructure coarsening before testing. Therefore, the fine grain structure capable of grain boundary sliding was considered to be always necessary for the high strain rate superplaticity.